The surface geology of the Walnut Gulch Experimental Watershed (WGEW), Tombstone, Arizona, is dominated by fan deposits, but in southern and southeastern parts of WGEW a complex history of tectonism has resulted in igneous-intrusive and volcanic rocks, and highly disturbed Paleozoic and Mesozoic rocks in the Tombstone Hills. Soils, which are dominantly sand and gravel loams that vary from deep and well drained to thin and immature, are reflective of the rocks on which they formed. Large landforms are mostly dissected pediments and erosion surfaces, and hills of the volcanic and carbonate rocks. Episodic faulting that began in Precambrian time has resulted in complex geologic and geomorphic conditions that remain poorly understood owing to Basin and Range structural and depositional processes. Small-scale landforms of the watershed are individual hills, undissected remnants of alluvial fans (fan terraces), basin floors, alluvial fans, and recent alluvial sediment of stream channels, flood plains, and terrace-inset deposits. This paper combines the results of previous studies with recent field investigations and analysis of aerial photography to yield a summary of watershed conditions in support of ongoing research.